In many organizations, wrist injury has become a major occupational health problem. An example is Carpal Tunnel Syndrome ("CTS"), one of the most frequently occurring cumulative injuries of the wrist. The carpal tunnel is a narrow fibrous tunnel, which is located on the palmar aspect of the wrist between the distal wrist flexion crease and, roughly, the center of the ulnar border of the thenar muscle mass.
Ten structures pass through the canal --four flexor superficialis tendons (flexor digitorum profundus tendons), the flexor pollicis longus tendons and the median nerve. The median nerve contains fibers from C5 to T1 spinal nerves with contributions from the upper, middle, and lower trunks of the brachial plexus. A part of the lateral and the medial brachial plexus cord combine to form the median nerve. The median nerve passes through the carpal tunnel as it supplies the hand. Distal to the carpal tunnel, the median nerve supplies a motor branch to the thenar muscles, flexor pollicis, and opponens pollicis muscles. Motor branches also supply the lateral head of adductor pollicis and the lumbrical muscles of the index and middle fingers.
Underlying the present invention is the recognition that repetitive and forceful flexion or extension movements of the wrist will gradually damage the median nerve in its narrow canal and lead to the increase of carpal canal pressure either by decreasing the diameter or by increasing the volume of contents of the tunnel. The use of the within inventive keyboard accessory has been found in practice to obviate Carpal Tunnel Syndrome in keyboard operators.
In the U.S. Pat. No. 360,529 issued to Jurey on Apr. 5, 1987, the wrists of a keyboard operator are projected through support loops C, supported from above on a frame A; and while supporting the weight of the wrists, the provided loops are uncomfortable, and to the extent that they resemble "shackles" are undesirable for modern usage.
In U.S. Pat. No. 591,800 issued to Finnblade et al on Oct. 12, 1897, wrist supports for a piano player are arranged for sliding movement on a transverse bar "d", but otherwise the individual wrist supports have no other degrees of movement, such as vertically ascending and descending movements, pivotal movements, or rotative movements, although position adjustments in the bar "d" are contemplated to partially overcome this shortcoming.
In U.S. Pat. No. 1,277,169 issued to Anderson on Aug. 27, 1918, a pair of arc-shaped hand rests are disclosed. Each hand rest has adjustable clamps to permit clamping of each hand rest to the front bar of a typewriter frame or to the edge of a table on which the typewriter is supported. Lateral movement of the hand rests is possible only by adjustment of set screws. The arm rests are connected to rods which have set screws thereon to permit vertical adjustment. The hand rests are flat and do not conform to the shape of the hand and the wrist.
In U.S. Pat. No. 1,801,669 issued to Hintz et al on Apr. 21, 1931, there is disclosed a hand rest for a typist which attaches to front bar frame of the typewriter. The hand rest is a single broad plate which extends the length of the typewriter. Neither horizontal, vertical nor pivotal movement of the hand rest is disclosed nor suggested.
In German patent 1,913,287 issued to Stegmann on Sep. 17, 1970, a typewriter attachment is disclosed having a base plate on which the typewriter rests. Two arms extend outwardly from the edges of the base plate, and threaded rods extend upwardly from each arm. A connecting rod is disposed between the threaded rods, and a broad cross-bar is received on the connecting rod. The single cross bar, serving as a support for the forearm of the user, can be vertically adjusted and can pivot about the connecting rod; but there is no lateral adjustment.
In German patent 2,430,036 issued to Coenen on Jan. 8, 1976, there is disclosed an arm support for typists which has a base on which a typewriter is disposed. A support extends from the base, and a vertically adjustable threaded rod is received in a complementary threaded nut, the nut being welded to the support preventing lateral movement. The top of the threaded rod is connected to an arm cushion which supports the entire forearm of the user, from the wrist to the elbow. This configuration increases stress on the flexor muscles in the forearm. The arm rest is not laterally adjustable with respect to the typewriter.
The applicant is also aware of the following references which are directed to arm rests for keyboards:
______________________________________ Inventor(s) Patent No. ______________________________________ Springer 4,621,781 Fowler et al 4,688,862 Berke 4,913,390. ______________________________________
However, none of the known references have considered the ergonomics involved in a person's using a keyboard. These references have not attempted to obtain a "transparent interface" between the user and the keyboard so that the user is operating at maximum efficiency and minimal fatigue and discomfort. The stress on the muscles of the forearm and ulnar deviation of the wrists have not been considered. In fact, most of the devices disclosed in the references aggravate the stress, rather than providing relief.
Accordingly, a keyboard accessory is needed so that the user and the keyboard cooperate as a single unit. In achieving this desired unity between the keyboard and its accessory, the anatomical operation of the fingers, the wrist and the arm muscles should be taken into account and integrated with knowledge of the movement of the anatomical members during keying operations. Further, consideration should be given to persons of varying heights and postures as well as keyboards of varying designs. In summary, a need exists for a device wherein ergonomics is a common denominator to integrate these factors to provide multiple degrees of freedom to the keyboard operator and to minimize stress on the wrists.